Pippa Middleton will compete in a gruelling 56-mile ski race to help fight children’s hunger.

Prince William’s sister-in-law is taking part in Sweden’s annual Vasaloppet cross-country ski race in aid of a charity providing breakfast to state primary school children.

The actress was gearing up to film her adaptation of Leo Tolstoy's masterpiece, in which she plays the title role, on location in the capital city of Moscow, but filmmaker Joe Wright decided he wanted a largely British production instead.

She explains, "It was pretty radical. We were going to St. Petersburg and Moscow. Then all of a sudden I got a call from Joe asking, 'Can you come round here please?' I live round the corner from him so he took me into his office and explained, 'There's been a bit of a change of plan.' He said, 'It's all set in a theatre now...' And the viewer watches the drama unfold as if sitting in the stalls."

Wright managed to transform a single sound stage in Surrey for scenes set in late-19th-century Russia, and Knightley hopes audiences will be impressed with his ambitious vision.

She adds, "What's the point of doing a safe adaptation? If you're going out you might as well go out with a bang."